8hp Merc starts great cold, not so much hot.

[flatbottomman]

My 8hp Mercury four stroke starts on the first pull cold. After I stop, I have to pull about a dozen times before it will actually run. The close it gets to the starting pull the more and more it starts seeming like it is going to run. I've tried choke in and out. Once it is started the motor runs great. Any ideas?

 

[thedude]

What year?

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[maintenanceguy]

Fuel injected or carburetor?

I'm guessing the mixture is too rich. When cold, the engine likes extra fuel - that's why carbs have a choke to block some of the air flow to increase the fuel:air ratio. But when hot, they don't like the extra fuel - which is why we don't need to choke a warm engine to get it to start.

I'm also guessing it has a carburetor and the idle air screw is turned too far out letting in too much fuel at idle. Too much fuel is good when the engine is cold. Too much fuel is not good when the engine is warm.

 

[1960 yellowboat]

Mercury=junk

 

[GYPSY400]

Mercury=junk

LOL.. I bet you think a evinrude four stoke is better?

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[GYPSY400]

Fuel injected or carburetor?

I'm guessing the mixture is too rich. When cold, the engine likes extra fuel - that's why carbs have a choke to block some of the air flow to increase the fuel:air ratio. But when hot, they don't like the extra fuel - which is why we don't need to choke a warm engine to get it to start.

I'm also guessing it has a carburetor and the idle air screw is turned too far out letting in too much fuel at idle. Too much fuel is good when the engine is cold. Too much fuel is not good when the engine is warm.

I agree.. it's getting too much fuel to start good when hot.

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